Files in current use are available in a variety of shapes and in varying grades of abrasive surfaces. Generally, these files are made with an abrasive surface consisting of a continuous run of teeth which are adapted for filing in only one direction. This type of file cannot simply be turned to use the other half because the teeth will be running in the wrong direction. Other files are made with an abrasive surface consisting of various grid grades of dispersed diamond particles. These files for the most part, have a flat elongated shape, a uniform thickness and have an abrasive surface consisting of one continuous grade of diamond grid. In some files, the upper side may have one abrasive grade and the bottom side another grade and some have two different grades on the same side.
A single file having four different grades of abrasive surfaces, two on each side, was not found in the prior art. Those files that did incorporate two grades of abrasive surfaces on one side were not offset above the longitudinal plane of the file base. By having the abrasive surfaces offset above the files longitudinal plane, as does the instant invention, better control is achieved since only the abrasive surface touches the area needing sharpening or shaping.
The prior art also did not disclose a file with a narrow non-abrasive center section having a pair of bores therethrough. The center section allows the file to be easily held and maneuvered in difficult to reach areas. The two bores, allow the file to be secured firmly to a work platform; or alternatively, to secure the file to one of the holes to allow the file to be rotated when necessary or, to attach a handle.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention, however, the following U.S. patents were considered related:
______________________________________ U.S. Pat. No. INVENTOR ISSUED ______________________________________ 4,584,745 Seiber 29 April 1986 3,369,283 Colding 20 February 1968 2,687,562 Noll 31 August 1954 2,308,624 Pouech 19 January 1943 633,523 Lytle 19 September 1899 ______________________________________
The Seiber patent discloses a file for sharpening saw teeth. The file includes a flattened oblong cross section having two sets of single cut teeth that extend over the file's longitudinal axis. A first set of teeth extends from a central lateral axis outward toward one end of the file; and a second set of teeth extends from the central axis outward towards the file's second end. The placement of the teeth allows the file to have an extensor cutting stroke using either end.
The Colding and Pouech patents each disclose methods for producing files having diamond particle abrasive surfaces.
The Colding patent discloses a cutting insert for chip cutting that consists of a metallic matrix with diamond particles. The particles cover at least ten percent of the edge surface. The diamond particles may be pressed in place or sprayed into the matrix, which is then hardened.
The Noll patent discloses a file especially suited to reconditioning disc type electrodes as used in welding machines. The file includes an elongated body of substantially uniform thickness. The body has a concave surface and is divided intermediate its ends into two working faces. Each working face has an arcuate, substantially parallel teeth that extend crosswise of the body and from centers approximately coincident with the longitudinal axis of the body. Each tooth of each working face has its cutting edge on the outer side of the arc and is directed towards the respective end of the body that defines one end of the corresponding working face.
The Pouech patent discloses a resilient nail file. The file has a metallic blank to a portion of which is adhesively secured diamond particles to form an abrasive surface. The adhesive is of a flexible type to permit the normal flexing of the resilient file without disrupting the adhesive with the consequent release of the diamond particles.
The Lytle patent discloses a horse hoof planar. The planar has a set of main teeth and auxiliary teeth or slits. Each of the main teeth consists of a vertical front face, an oblique rear face that meets the front face at the cutting edge, which extends transversely across the planar. The planar includes a curved or rounded throat between the front face of one tooth and the rear face of the next tooth in advance. This grooved throat causes the planing that are cut by the teeth to pass down their front walls through the grooved throats and be thrown out by the walls of the teeth next in front. Thus, the specific construction of the throats of the teeth causes the planar to be self clearing.